Generally, variable gain amplifiers (VGA: Variable Gain Amplifier) have been widely used in digital demodulation circuits. Digital demodulation circuits demodulate digital signals from modulated waves which are produced by modulating carrier waves with digital signals.
Patent Literatures 1, 2 disclose technologies compensating for temperature variations in digital demodulation circuits. Patent Literature 1 discloses a temperature compensation method for an automatic gain control circuit (AGC: Automatic Gain Control), which corrects temperature detected by a temperature sensor so as to apply it to a baseband process in a communication device. Patent Literature 2 discloses a temperature compensation method adapted to a digital wireless terminal, which achieves temperature compensation for amplifier-gain parameters in an analog processing part by use of a parameter memory device of a digital processing part.
In the technologies of Patent Literatures 1, 2, temperature correction data, corresponding to temperature information, have been stored in a memory device in advance, and therefore CPU processing is performed to read temperature correction data from the memory device, thus achieving temperature compensation for control values applied to a variable gain amplifier.